(i) Field of the Invention
The present invention relates to novel diaminoindane derivatives and a process for the preparation thereof. The diaminoindane derivatives of the invention are useful as raw materials for isocyanates, epoxy resins, bismaleimides and the like and also as curing agents for isocyanates, for example, RIM urethanes. The diaminoindane derivatives can also be used as curing agents for epoxy resins and bismaleimides and can be added as modifiers to various resins, rubbers and the like.
(ii) Description of the Related Art
Diamine compounds which have been used for the above-described applications prior to the present invention include bis(4-aminophenyl)methane; 2,4-diamino-3,5-diethyltoluene and 2,6-diamino-3,5-diethyltoluene (hereinafter "DETDA" collectively); 2,4-diamino-5-tert-butyltoluene and 2,6-diamino-3-tert-butyltoluene (hereinafter "t-BTDA" collectively).
Bis(4-aminophenyl)methane (hereinafter "MDA") has been prepared by the condensation of aniline with formaldehyde.
As disclosed in U.S. Pat. No. 4,219,502 and European Patent No. 177,916 DETDA and t-BTDA have been prepared by ethylating or tert-butylating 2,4-diamino-toulene or 2,6-diaminotoluene.
The above diamines have both benefits and disadvantages in handling, properties and preparation. For example, bis(4-aminophenyl)methane is economical but has disadvantages such as a high melting point and does not form a homogeneous mixture. It is accompanied by a further drawback that it is unstable to heat, light and oxygen in air, and when employed as a curing agent, the curing reaction proceeds too quickly.
On the other hand, DETDA and t-BTDA which have been prepared by alkylation of diaminotoluenes are generally in a liquid form and enjoy easy handling. Their use as curing agents for RIM urethanes is however accompanied by the drawback that curing proceeds too quickly with DETDA and too slowly with t-BTDA.